Access floors, also known as sectional false floors, consist mainly of floor panels laid edge to edge and carried on height-adjustable load-bearing supports which are set out in a regular grid and stand on a subfloor or structural slab. Such access floors are provided mainly in buildings for office, administrative, industrial, commercial, and trade use, in order to allow use of the void under the floor panels for free layouts of a wide variety of services: electrical mains, telephone, control, and data cables; pipework and ducting for ventilation, air conditioning, heating, hot and cold water supply, and the like. The floor panels can be lifted out separately and provide ready access to such installations, allowing them to be modified at any time to adapt to changes in user requirements.
Conventional procedures of installing and laying access floors are extremely laborious and time-consuming, and high labour costs make them correspondingly expensive. Structural slabs and subfloors are built to large tolerances and are usually far from level, smooth, or even. Such unevenness and differences in level have to be compensated when the supports or feet are set out or fitted to carry the floor panels, so as to form an accurate, perfectly horizontal bearing plane at the proper height for the floor panels. Conventional procedures require the subfloor to be accurately measured and the grid laid out on it; each support must then be positioned on the subfloor at a grid intersection, secured in place, and its height accurately adjusted. Despite unevenness in the subfloor, each support must stand absolutely plumb on its grid point; for this purpose, its foot has to be wedged up or the support has to be provided with some form of movable joint. All the supports known to date have screw threads to permit height adjustment. Usually, the height is adjusted by using of a floor panel which is laid across adjacent supports already adjusted and the new support to be set up; the panel is then checked by means of a spirit-level. This procedure requires the heavy floor panels to be removed and replaced repeatedly. To date, therefore, the assembly of access floors has been an extremely laborious task that demands heavy physical labour at or near floor level and makes only slow progress even when carried out by skilled workers.